Nowadays, cloud computing has become a common provision for information network construction in enterprises, and virtualization technology may be commonly employed and deployed in cloud computing. Currently, Software Defined Network (SDN) may be a prevailing solution for virtualization. And, by deploying a control plane of a network, such as various policies for all kinds of forwarding behaviors in a centralized controller. SDN may separate the control plane from a forwarding plane of the network, and thus a forwarding device may forward a flow according to a flow table distributed from the controller.